Since GTK+ 3.3.18, GDK_SCROLL_MASK has been used as the mask for scroll
events. Update the documentation to reflect this.
https://bugzilla.gnome.org/show_bug.cgi?id=677339
* button press events for buttons 4 and 5 when the wheel is turned.
*
* To receive this signal, the #GdkWindow associated to the widget needs
- * to enable the #GDK_BUTTON_PRESS_MASK mask.
+ * to enable the #GDK_SCROLL_MASK mask.
*
* This signal will be sent to the grab widget if there is one.
*